New vehicle multidisplacement or cylinder shut off engines are now in development and in some cases in production. These engines are essentially designed to shut off one-half of the number of cylinders when operated in slow speed or idling situations in which the power output of all the cylinders is not needed. In slow speed situations, this shut off capability results in higher overall gas mileage as, for example, an eight cylinder engine consumes fuel at a four cylinder rate. Multidisplacement engines can be eight cylinders shutting off four cylinders, six cylinders shutting off three cylinders, ten cylinders shutting off five cylinders, etc. In the discussion below, an eight cylinder multidisplacement engine is described, but it should be realized that the same discussion will apply to all multidisplacement engines.
One problem presented by multidisplacement engines is the need to quickly supply an adequate power flow or torque flow from the engine to the transmission. By power or torque flow is meant the direction of movement of rotational power from the engine to the transmission. In contrast to standard engines that always utilize all the cylinders, multidisplacement engines use only half the total number of cylinders when at idle or very slow speeds. Consequently, one problem presented by the multidisplacement engines is the need to establish a quick increase in power flow when moving from an idle to running condition.
It is well known to insert a torque converter between an internal combustion engine and an automatic transmission to increase the torque supplied to the transmission which allows for efficient starts from a stopped position. The torque converter comprises two housing shells interconnected to retain transmission fluid. The shell on the engine side is connected to the engine through a flywheel or similar device to transmit the rotary motion of the engine crankshaft to the two shells. Pump vanes are incorporated into the shell on the transmission side of the torque converter which, when rotated by the connection to the engine, causes a toroidal flow to the oil present in the converter. The oil flow acts on a turbine, which also has corresponding vanes, to rotate the turbine. The turbine is connected to a stator which is configured to direct flow to the pump.
Since slippage always exists between the pump and turbine, which results in loss of efficiency, it is well known to supply a lock-up clutch to a torque converter to create a nonrotatable connection between the housing shells and the transmission input shaft
There are examples in the prior art of the use of torque multiplier devices that employ clutches operatively connected to planetary gears in place of the torque converters described above. U.S. Pat. No. 5,836,849 to Mathiak, et al. discloses an apparatus which uses a friction clutch to transmit initial torque to an automatic transmission. Electronic controls are used to control the clutch. U.S. Pat. No. 5,846,153 to Matsuoka discloses a double clutch system with planetary gears placed between an engine and a manual transmission. The clutches are used to increase the number of gears provided to two different power paths. U.S. Pat. No. 6,406,400 to Shih discloses a planetary gear arrangement that replaces a conventional clutch and gearbox. The transmission input shaft is directly coupled to the engine by a flywheel or other convenient device. Gear shifting is performed by the electronically controlled disengagement of the clutch to allow a manual gear change maneuver. U.S. Pat. No. 6,849,024 to Hayashi, et al. discloses a clutch assembly having a starting clutch and a second clutch to transfer power to an intermediate portion of the planetary mechanism. U.S. Pat. No. 5,019,022 to Uhlig, et al. provides a speed change arrangement in which a disc brake and disc clutch are alternately engaged by a hydraulically operated toothed disc support to create two different sun gear connections—either to another planet gear to create a direct (1:1 ratio) drive power flow connection between the engine and the transmission or to the clutch housing. U.S. Pat. No. 5,628,703 discloses a flywheel-clutch arrangement for a manual gearbox in which when the clutch is engaged, the planetary gears are disengaged from the drive train. When the clutch is disengaged, the planet system is driven by the flywheel to aid synchronization. Finally, United States Patent Publication No. 2006/0016661 to George, et al., which is hereby incorporated by reference, discloses a device for producing an operative connection between an internal combustion engine and a transmission. The device is configured to be used with a wet clutch—planetary gear system and sized to easily replace, as in a drop-in, a standard torque converter.
Most of the cited references are designed to be used in conjunction with a manual transmission. As discussed above, clutch type torque multipliers are designed to promote efficiencies in power flow, and, with the exception of the '661 publication, they do not disclose a system in which the torque multiplier can easily replace a typical torque converter. Moreover, none have been disclosed as compatible with multidisplacement engines.
The operation of cylinder shut off engines also presents a unique challenge in overcoming the vibration/resonance that is created during drive train operation. As part of the drive train, the torque converter is subject to this vibration. Dampers are often employed to absorb the vibration and allow the torque converter and drivetrain to operate smoothly. However, in multidisplacement engines, two sources of vibration exist—one generated from four cylinder operation and a second generated by eight cylinder operation.
Thus, there is a need in the industry for a clutch type torque multiplier that is compatible with a multidisplacement engine and that can withstand two modes of vibration generated by two different sets of operation characteristics.